title: Spectroscopic characterization of extracellular polymeric substances from Escherichia coli and Serratia marcescens: suppression using sub-inhibitory concentrations of bismuth thiols.
abstract: Free and bound (or capsular) EPS produced by suspended cultures of Escherichia coli and Serratia marcescens were characterized in detail using colorimetric analysis of total proteins and polysaccharides, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy (AES) in the presence and absence of bismuth-based antifouling agents. Subtle differences in the chemical composition of free and bound EPS were observed for both bacteria in the absence of bismuth. Total polysaccharides and proteins in free and bound EPS decreased upon treatment with subinhibitory concentrations of lipophilic bismuth thiols (bismuth dimercaptopropanol, BisBAL; bismuth ethanedithiol, BisEDT; and bismuth pyrithione, BisPYR), with BisBAL being most effective. Bismuth thiols also influenced acetylation and carboxylation of polysaccharides in EPS from S. marcescens. Extensive homology between EPS samples in the presence and absence of bismuth was observed with proteins, polysaccharides, and nucleic acids varying predominantly only in the total amount produced. Second derivative analysis of the amide I region of FTIR spectra revealed decreases in protein secondary structures in the presence of bismuth thiols. Hence, antifouling properties of bismuth thiols appear to originate in their ability to suppress O-acetylation and protein secondary structure formation in addition to free and bound EPS secretion.
authors.affiliation: Department of Civil and Environmental Engineering, University of Houston, Houston, Texas 77204-4003, USA.
authors.forename: Appala Raju
authors.initials: AR
authors.lastname: Badireddy
authors.forename: Bhoom Reddy
authors.initials: BR
authors.lastname: Korpol
authors.forename: Shankararaman
authors.initials: S
authors.lastname: Chellam
authors.forename: Paul L
authors.initials: PL
authors.lastname: Gassman
authors.forename: Mark H
authors.initials: MH
authors.lastname: Engelhard
authors.forename: Alan S
authors.initials: AS
authors.lastname: Lea
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Rosso
mesh_terms: D000107:Acetylation; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000032:analysis* / Q000187:drug effects; D001729:Bismuth / Q000494:pharmacology*; D004926:Escherichia coli / Q000737:chemistry*; D011135:Polysaccharides, Bacterial / Q000032:analysis* / Q000187:drug effects; D017433:Protein Structure, Secondary; D012706:Serratia marcescens / Q000737:chemistry*; D013057:Spectrum Analysis; D013438:Sulfhydryl Compounds / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D011135:Polysaccharides, Bacterial; D013438:Sulfhydryl Compounds; D001729:Bismuth